1. Field of the Invention
The present invention relates to a safety switching device for use with power equipment, such as power tools. An operator of such power equipment may unplug or remove the power source from the power equipment without turning the power equipment off directly. This removal of the power source could be caused accidently or otherwise; however, when the operator plugs the equipment back in or returns power to the equipment by other than the on/off switch of that piece of equipment, a hazardous situation exists. This is because the equipment may restart unexpectedly. Accordingly, use of the present invention with a power equipment prevents the hazardous situation from occurring.
2. Description of the Prior Art
The Electric safety Switch Circuitry described by Yutaka Irie et al. in U.S. Pat. No. 4,048,666 discusses an ON/OFF switch located between a power source and a transformer and the ON/OFF switch connected in a low voltage circuit after the transformer. An OFF switch is normally closed and an ON switch is normally open. Depressing the ON switch will cause the low voltage circuit to be complete thereby activating a relay. The relay will cause several switches to close thus providing high voltage to power equipment. Further, the relay causes another switch to close in order to maintain the low voltage circuit in a conducting mode. Once power is removed from the system or the OFF switch is depressed the relay will no longer receive a low voltage, and each of the switches will open their respective circuits. Once power is restored to the circuit the relay will not close the switches again until an the switch is again depressed, to thereby re-energize the power equipment. Further provide safety switches are responsive to abnormal conditions being monitored in the power equipment.
The Safety Control System described by Harold T. Hagfors in U.S. Pat. No. 3,371,254, the Magnetic Loom-Brakin Device discussed in U.S. Pat. No. 3,636,375 to Stanley E. Armstrong, and the Magnetic Switch and Circuitry for Safety Shut Down of Power Equipment depicted in U.S. Pat. No. 4,068,274 to Frank W. Murphy, Jr. et al. are representative of other known arrangements using safety electromagnetic switches to control equipment.